DB2 Backup vs Compress backup

hi,

DB2 9.7 fp 4 /Win 2008 R2 (8GB RAM / 6 CPU)

I take daily online database backup (only 1 database, 500GB size) and it takes around 50 minutes.
It is Unthrottled backup. The backup command i use is :

BACKUP DATABASE MYDB ONLINE TO X:\DB2BACKUP INCLUDE LOGS WITHOUT PROMPTING;

As the Database grows faster, I need big disk space to store the backup file.
So, I use the COMPRESS command to take a backup. But not it takes 3 hours to complete the backup and compredd around 65%.

Is there any way to speed up the backup (I am looking to do under 2 hours)

Any suggestions .....

Thanks in advance.